Abstract: The error diffusion algorithm performs well as one of Frequency Modulation (FM) halftoning methods, except for tending to producing worm artifacts on highlight areas and generating noises which blur the edge of images. A new error diffusion algorithm based on the average threshold was proposed by changing scanning order. Using adaptive threshold based on spatial extension, the halftoning images were obtained by optimizing threshold and using a serpentine scanning. The experimental results show that the proposed algorithm can reduce artifacts, enhance edge of images, and give an appeasing perception.

Key words: digital halftoning, error diffusion, dynamic threshold, scanning order

摘要： 误差扩散是一种非常优秀的调频半色调技术，但这种方法在图像高光和暗调以及阶调平滑区域会产生“蠕虫”，同时噪声较多，导致半色调图像的边缘不清晰。在Floyd和Steinberg的误差扩散算法的基础上，设计一种新的基于平均阈值和改变扫描路径的误差扩散算法——阈值采用平均值法，通过优化平均阈值方法中的γ值得到最优的半色调图像，同时扫描路径采用“蛇型”路径。实验结果表明该算法可以减少“蠕虫”，增强图像的边缘，提高半色调图像的主观视觉效果。

关键词: 数字半色调, 误差扩散, 动态阈值, 扫描顺序